Card reader systems are known in which a card reader is programmed to provide an output signal once an appropriately encoded card is presented to the reader, the output signal being used, e.g. to open a door. These systems may be electrical, optical, mechanical, magnetic or electronic. However, the cards presently used in such systems have to be presented to the reader in a particular way, for example, the card having to be a certain way up and with a given end presented to the reader first. This is inconvenient and, e.g. leads to user dissatisfaction, especially with non-constant users, e.g. hotel guests. The available added security of card-access systems is undermined by their difficulty of use in an unsupervised environment by an unskilled user, the casual guest.
We have now found that, with careful design of how encoding is put on to a card, these problems may be overcome, and easy to use secure card access made possible.